Photon-echo detected nuclear quadrupole resonance spectroscopy

Rare-earth-ion-doped crystals (REICs) have played an important role in quantum information processing due to their excellent coherent properties. In order to obtain the information regarding the hyperfine structures of the rare-earth ions in REICs, optically detected nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) techniques based on RF resonance and various optical detection methods are widely employed in previous works. Here we demonstrate a new method of NQR spectroscopy based on the photon-echo detection. The hyperfine spectra of the ground state (⁷F₀) and the optically-excited state (⁵D₀) of ¹⁵¹Eu³⁺ in Y₂SiO₅ at zero field are obtained. This method can determine the hyperfine splittings within the ground state and the optically-excited state and is shown to be robust against electrical noise. Our results provide an alternative way for optical detection of NMR and NQR with high signal-to-noise ratio.     

Linear free‐energy relationships in semiquinone species and their Mn(II) and Cu(II) complexes

Linear free‐energy relationships for a series of functionalized semiquinone ligands and their Mn^II‐ and Cu^IIhydro‐tris(3‐cumenyl‐5‐methylpyrazolyl) borate complexes were examined. Quinone–semiquinone cycle half‐wave reduction potentials and semiquinone hydrogen hyperfine coupling constants (a_H) were determined and their correlation with Hammett σ parameters reported. A new σ parameter, σ_aH, has been proposed. Mn^II and Cu^II metal complex metal–ligand charge transfer and n → π* UV transitions were found to be modulated by substituents. Satisfactory Hammett correlations between UV transitions and various σ values have been determined and compared in a number of instances. Copyright © 2011 John Wiley & Sons, Ltd.     

Sn and Sn hyperfine structure in the rotational spectrum of tin monosulfide recorded using laser ablation-source equipped, chirped-pulse Fourier transform microwave spectroscopy

Tin metal has been ablated with pulsed radiation from a Nd:YAG laser (λ=1064 nm). Carbonyl sulfide, diluted in high pressure argon, has been pulsed into the resultant Sn plasma. One of the results of this experiment has been the production of SnS. These events have allowed a rotational spectrum of tin monosulfide to be studied using a chirped-pulse Fourier transform microwave spectrometer. The resolution of the spectrum obtained was sufficient to observe hyperfine structure from the ¹¹⁷Sn and ¹¹⁹Sn-containing SnS molecules. Tin nuclear spin-rotation hyperfine constants are reported for the first time.     

Born-Oppenheimer breakdown effects and hyperfine structure in the rotational spectra of SbF and SbCl

Pure rotational spectra have been measured for the ground electronic states of SbF and SbCl. The molecules were prepared by laser ablation of Sb metal in the presence of SF₆ or Cl₂, respectively. Their spectra were measured with a cavity pulsed jet Fourier transform microwave spectrometer. Although both molecules have two unpaired electrons, they are subject to Hund’s coupling case (c), and have X₁0⁺ ground states. The spectra have been interpreted with the formalism of ¹Σ⁺ molecules. For both molecules spectra of several isotopomers have been measured in the ground and first excited vibrational states. Large hyperfine splittings attributable to both nuclear quadrupole coupling and nuclear spin-rotation coupling have been observed. A Dunham-type analysis has produced unusually large Born-Oppenheimer breakdown parameters, which are interpreted in terms of the electronic structures of the molecules.     

Mössbauer spectroscopic studies of [Fe(H2O)6]3+ in amorphous frozen solutions at weak applied magnetic fields

The ferric hexaquo complex, [Fe(H₂O)₆]³⁺, has been studied by Mössbauer spectroscopy of amorphous aqueous frozen solutions at weak applied magnetic fields. Spectra of well resolved paramagnetic hyperfine structure have been interpreted in terms of a spin Hamiltonian model for the crystal field interaction proposed in a previous work. Reasonable fits could be obtained only by the addition of a random magnetic field of a few Gauss which is attributed partly to the dipolar interaction with neighbouring iron ions, and partly to the ligand hyperfine interaction.     

Pressure broadening by argon in the hyperfine resolved P(10) and P(70) (17,1) transitions of I2 XΣ(0g)→BΠ(0u) using sub-Doppler laser saturation spectroscopy

The dependence of pressure broadening upon hyperfine component in the P(10) and P(70) lines of the (17,1) band of the I₂ X¹Σ(0_g⁺)→B³Π(0_u⁺) has been studied using laser saturation spectroscopy. By limiting absorption to the zero velocity group, Doppler broadening is removed, lineshapes with widths (FWHM) <9 MHz are detectable, and collision-induced broadening is measured at pressures of 0.2-1.2 Torr. The rates for broadening by argon are 8.3±0.3 and 10.7±0.4 MHz/Torr for the P(70) and P(10) lines, respectively. No significant variation in broadening rates is observed for the 15 hyperfine components of these even rotational lines. The effects of velocity cross-relaxation introduce a broad baseline into the spectra, which is strongly dependent on rotational state, pressure, and laser modulation frequency. The observed broadening rates correlate well with prior measurements and the polarizability of the collision partner.     

Hyperfine splitting and isotope shift in the atomic D2 line of 22,23Na and the quadrupole moment of 22Na

The hyperfine structure of the D₂ optical line in ²²Na and ²³Na has been investigated using high resolution laser spectroscopy of a well-collimated atomic beam. The hyperfine splitting constants A and B for the excited 3p ²P_3/2 level for both investigated sodium isotopes have been obtained. They are as follows: A(22) = 7.31(4) MHz, B(22) = 4.71(28) MHz, A(23) = 18.572(24) MHz, B(23) = 2.723(55) MHz. With this data, using the high precision MCHF calculations for the electric field gradient at the nucleus, the electric quadrupole moment of ²²Na has been deduced: Q_s(22) =+0.185(11) b. The sign of Q_s(22), determined for the first time, indicates a prolate nuclear deformation. A precise value of the isotope shift ^22,23Na in the D₂ line has also been obtained. Received: 26 February 1998 / Revised version: 25 June 1998     

Negative 4ƒ-induced hyperfine field on samarium in paramagnetic Eu(Sm)Al2

The hyperfine field at samarium nuclear site induced by the paramagnetism of 4? electrons has been measured in Eu(Sm)Al₂ using perturbed angular correlation technique and found to have a negative sign which is in striking contrast to the positive sign expected in free Sm³⁺ ion. It amounts to a large negative Knight shift at samarium nuclear site in this alloy.     

Hyperfine structure and isotope shifts in the 5d6s2 a2D3/2--5d6s(a3D)6p z4F5/2 ° transition of Hf II

The hyperfine structure and isotope shifts of the transition between the 5d6s² a²D_3/2 ground state and the 5d6s(a³D)6p z⁴F_5/2 ^° excited state of singly ionized hafnium at \lambda=340 nm have been investigated by laser spectroscopy using a radio-frequency quadrupole ion trap. The magnetic dipole coupling constant A and electric quadrupole coupling constant B of the two atomic levels for both stable isotopes ¹⁷⁷Hf and ¹⁷⁹Hf are determined. The changes of mean square nuclear charge radii \delta[ r²] of the stable Hf isotopes and the radioactive isotope ¹⁷²Hf (T_1/2=1.87a) have been extracted from the data. This revised version was published online in August 2006 with corrections to the Cover Date.     

Influence of the local environment on the hyperfine interactions in Zr(Fe1-xCox)2 compounds

Ferromagnetic Laves phase compounds Zr(Fe_1-xCo_x)₂ have been investigated by means of the Mössbauer effect (⁵⁷Fe) and by the time-dependent perturbed angular correlation of \gamma -rays (¹⁸¹Ta) technique. It has been concluded from ME experiments that by exchange of Fe by Co in the nearest neighbour shell of the nuclear probe the hyperfine magnetic field acting on ⁵⁷Fe decreases by 10--12 kG. The analysis of the TDPAC experiments revealed that two different hyperfine magnetic fields: B₁ ^hf(Ta)~ 61 kG and B₂ ^hf(Ta)~ 88 kG act on the ¹⁸¹Ta nuclei. Both have a negative sign.     

Frequency (field) dependent NMR relaxation rate in the interrupted metallic strand model

We calculate the nuclear magnetic resonance rate T^?1₁ arising from the electron-nuclear hyperfine contact interaction, within the interrupted metallic strand model. The electron levels are assumed to have an energy half width Γ and a mean spacing Δ₀ and it is assumed that all segments have the same nuclear spin temperature. In the limit Γ ? Δ₀, T^?1₁ has nearly the same behaviour for kT ? Δ₀ and kT?Δ₀. It is proportional to temperature but has a Lorentzian magnetic field dependence with halfwidth H= Γ/μ_B. At low fields it is enhanced over the value for a normal metal by the factor Δ₀/Γ.This anomalous behaviour arises from the suppression of electron spin flip processes by a magnetic field and should always occur when electronic states are localised, that is when there is a locally discrete electron energy spectrum. Therefore it may be relevant not only to certain linear chain conductors but to other cases of electron localisation.The present model provides an additional possible source of frequency dependence of T₁ in linear chain materials. In certain materials especially those containing defects, it may be more appropriate than the currently accepted mechanism which involves electron spin diffusion in one dimension.     

Nuclear hyperfine effects in Dy(OH)3

A crystal field analysis of the experimental data on magnetic, optical and thermal properties of Dy(OH)₃ single crystals have been published The nuclear hyperfine properties of Dy³⁺ in Dy(OH)₃ were studied using a crystal field thus obtained. The hyperfine spectra were computed from 4–20 K with a minimum number of approximations. Under a weak crystal field, the lowest electronic level is a Kramers' doublet For this highly anisotropic crystal, the magnetic hyperfine and the quadrupole interactions are both prominent The quadrupole interaction energy is temperature dependent The value of the magnetic Sternheimer factor R_hf/R is determined to be 0 14 The observed specific heat $\text{C}{}_{\mathrm{hf}}\text{R}$ arising from hyperfine interactions have been explained satisfactorily A maxima is expected at 21 mK.     

121,123Sb and 75As NMR and NQR investigation of the tetrahedrite (Cu12Sb4S13) – Tennantite (Cu12As4S13) system and other metal arsenides

This work is motivated by the recent developments in online minerals analysis in the mining and minerals processing industry via nuclear quadrupole resonance (NQR). Here we describe a nuclear magnetic resonance (NMR) and NQR study of the minerals tennantite (Cu₁₂As₄S₁₃) and tetrahedrite (Cu₁₂ Sb₄S₁₃). In the first part NQR lines associated with ⁷⁵As in tennantite and ^121,123Sb isotopes in tetrahedrite are reported. The spectroscopy has been restricted to an ambient temperature studies in accord with typical industrial conditions. The second part of this contribution reports nuclear quadrupole-perturbed NMR findings on further, only partially characterised, metal arsenides. The findings enhance the detection capabilities of NQR based analysers for online measurement applications and may aid to control arsenic and antimony concentrations in metal processing stages.     

The Lamb-dip spectrum of methylcyanide: Precise rotational transition frequencies and improved ground-state rotational parameters

Methylcyanide, CH₃CN, is an important interstellar species, and therefore the accurate knowledge of precise rest frequencies for rotational transitions as well as ground-state rotational and hyperfine constants is needed. In this work the hyperfine structure of the millimeter- and submillimeter-wave spectra of CH₃CN has been further investigated. In addition, accurate THz measurements have been carried out for the first time. Consequently, the present investigation allowed us to provide the most accurate ground state rotational and hyperfine parameters known at the moment for CH₃C¹⁴N. To resolve the hyperfine structure of the rotational transitions observed, the Lamb-dip technique has been exploited. Both frequency-modulated and video-type detections have been employed.     

The C hyperfine constants of HCS and HSC studied by microwave spectroscopy

The ¹³C hyperfine constants of the H¹³CS and HS¹³C radicals are determined by microwave spectroscopy. For H¹³CS, the 1₀₁-0₀₀ rotational transition is measured at 38.5 GHz with a Fourier transform microwave spectrometer, and two ¹³C hyperfine constants are determined. They are well interpreted in terms of a relatively large HCS bonding angle (132.8°). For HS¹³C, the N=7-6, 9-8, and 10-9 rotational transitions are measured in the 268-384 GHz region by using a source modulation spectrometer combined with a free-space discharge cell, and five ¹³C hyperfine constants including the nuclear spin-rotation constant, C_aa, are determined. From the ¹³C hyperfine constants, the p character of the unpaired electron orbital on the carbon atom is estimated to be 66.5%, supporting a classical resonance picture; .     

An analysis of the rotational, fine and hyperfine effects in the (0, 0) band of the AΠ-XΣ transition of manganese monohydride, MnH

High-resolution (±0.003 cm⁻¹), laser induced fluorescence (LIF) spectra of a supersonic molecular beam sample of manganese monohydride, MnH, have been recorded in the 17500-17800 cm⁻¹ region of the (0, 0) band of the A⁷Π-X⁷Σ ⁺ system. The low-N branch features were modeled successfully by inclusion of the magnetic hyperfine mixings of spin components within a given low-N rotational level using a traditional ‘effective’ Hamiltonian approach. An improved set of spectroscopic constants has been extracted and compared with those from previous analyses. The optimum optical features for future optical Stark and Zeeman measurements are identified.     

Nuclear magnetic resonance of oriented54Mn nuclei in antiferromagnetic MnCl2 · 4H2O

Nuclear magnetic resonance of oriented⁵⁴Mn nuclei in antiferromagnetic MnCl₂ · 4H₂O has been observed. The first two lines of the sextuplet split by quadrupole interaction are at frequencies 500.4 and 514.7 MHz, implying a hyperfine field of 643(5) kG. The stronger line at 500.4 MHz has a half-width at half maximum of 60 kHz and is shifted downward and split in frequency on application of a magnetic field. The nuclear spin-lattice relaxation time is dependent both on the applied field and the size and/or quality of the crystal.     

Fourier transform microwave spectroscopy of aluminum hydrosulfide, AlSH

Pure rotational transitions of three isotopic species of aluminum hydrosulfide, AlSH, have been measured with a cavity pulsed jet Fourier transform microwave spectrometer. AlSH was prepared by the reaction of laser ablated Al metal with H₂S, and was stabilized in pulsed supersonic free jets of Ar. For each species the transition 1₀₁-0₀₀ was measured; hyperfine structure due to the nuclear spin of ²⁷Al was observed for the first time and analyzed. For Al³²SH and Al³²SD, the rotational constants are in excellent agreement with published values. For the third species, Al³⁴SH, this is the first observation, and its rotational constants are consistent with the published geometry. Information on the electronic structure of the molecule has been obtained using the ²⁷Al nuclear quadrupole coupling constants and nuclear spin-rotation constants. The latter have been used to evaluate ²⁷Al NMR shielding parameters, which are compared with those of other ²⁷Al compounds. These shieldings have been found to be in excellent agreement with theoretical predictions. The results should also help facilitate astrophysical searches for the molecule.     

FTMW spectroscopy of jet-cooled 9-cyanoanthracene

Rotational spectrum of jet-cooled 9-cyanoanthracene has been observed in the 4-8 GHz region with a Fourier-transform microwave spectrometer. The present observation of 25 low-J transitions with J^′′?11 has confirmed the previous results on the rotational constants of the ground state determined by rotational coherence spectroscopy [J. Phys. Chem. A. 105 (2001) 1131] and provided the values with significantly improved precision. An accurate set of hyperfine splitting constants is also reported for the ¹⁴N nuclear quadrupole coupling. The electric dipole moment was determined from Stark effect measurements on several split components: μ_b(=μ)=4.406(7) D.     

Nuclear magnetic resonance and transferred hyperfine interaction study of the crystallographically inequivalent Cs(I) and Cs(II) in a Cs2CuCl4 single crystal

¹³³Cs (I=7/2) nuclear magnetic resonance in a Cs₂CuCl₄ single crystal grown by using the slow evaporation method was measured in its three mutually perpendicular crystal planes. The ¹³³Cs resonances of two different groups with two crystallographically inequivalent cesium nuclei, Cs(I) and Cs(II), in the unit cell were recorded. The transferred hyperfine fields for Cs(I) and Cs(II) calculated from the paramagnetic shift and the molecular susceptibility measurements could be expressed by the linear equation H_hf=AT+B. The angular dependence of the ¹³³Cs nuclear magnetic resonance spectra showed that the Cs(I) and the Cs(II) nuclei had different values for the quadrupole coupling constant. The electric field gradient tensors of Cs(I) and Cs(II) were symmetric, and the orientations of their principal axes did not coincide. The Cs(I) ion surrounded by 11 chlorine ions had a small quadrupole parameter, a smaller charge distribution, and a small value for the transferred hyperfine field. However, the Cs(II) ion surrounded by nine chlorine ions had a larger quadrupole parameter, a larger charge distribution, and a larger value for the transferred hyperfine field.